Study links tobacco use to gene changes, cancer risk

12/27/2012 12:00 AM

12/26/2012 3:00 PM

Cigarettes leave you with more than a smoky scent on your clothes and fingernails. A new study has found strong evidence that tobacco use can affect the activity of genes known to increase the risk of developing cancer. The finding may give researchers a new tool to assess cancer risk among smokers.

DNA isn't destiny. Chemical compounds that affect the functioning of genes can bind to our genetic material, turning certain genes on or off. These so-called epigenetic modifications can influence a variety of traits, such as obesity and sexual preference.

In the new study, published in Human Molecular Genetics, researchers analyzed epigenetic signatures in blood cells from 374 individuals enrolled in the European Prospective Investigation into Cancer and Nutrition. EPIC, as it's known, is a massive study aimed at linking diet, lifestyle, and environmental factors to the incidence of cancer and other chronic diseases.

Half of the group consisted of people who went on to develop colon or breast cancer 5 to 7 years after first joining the study, whereas the other half remained healthy.

The team, led by James Flanagan, a human geneticist at Imperial College London, discovered a distinct "epigenetic footprint" in study subjects who were smokers. Compared with people who had never smoked, these individuals had fewer chemical tags known as methyl groups – a common type of epigenetic change – on 20 different regions of their DNA.

When the researchers extended the analysis to a separate group of patients and mice that had been exposed to tobacco smoke, they narrowed down the epigenetic modifications to several sites located in four genes that have been weakly linked to cancer before. All of these changes should increase the activity of these genes, Flanagan said. It's unclear why increasing the activity of the genes would cause cancer, he said, but individuals who don't have cancer tend not to have these modifications.

The work may lead to new ways to assess cancer risks from smoking. The new study, Flanagan said, may make it possible for doctors to quantify a person's cancer risk simply through an epigenetic analysis of their DNA.

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